Git

A cloud service for remote hosting of git repositories. In addition to hosting
your code, the site helps manage software development projects with features like
issue tracking, collaborating with other GitHub users, and hosting web pages.

GitHub offers free services for open source projects (accessible to the public) and
paid tiers for private projects. For public projects, anyone can see code you push to
GitHub and offer suggestions, or even code, to improve your project. GitHub currently
hosts the source code for tens of thousands of open source projects, but is not alone.
BitBucket and GitLab.com offer
comparable services.

GitLab (a cloud service a lot like GitHub) comes in two flavors, a publically available
cloud service and a cloud service for SESYNC science
teams. Use the SESYNC server https://gitlab.sesync.org to host private projects shareable
with other SESYNC users.